Patch "iommu/arm-smmu-v3: Cope with duplicated Stream IDs" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

iommu/arm-smmu-v3: Cope with duplicated Stream IDs

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
iommu-arm-smmu-v3-cope-with-duplicated-stream-ids.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Robin Murphy <[email protected]>
Date: Tue, 2 Jan 2018 12:33:14 +0000
Subject: iommu/arm-smmu-v3: Cope with duplicated Stream IDs

From: Robin Murphy <[email protected]>

commit 563b5cbe334e9503ab2b234e279d500fc4f76018 upstream.

For PCI devices behind an aliasing PCIe-to-PCI/X bridge, the bridge alias to DevFn 0.0 on the subordinate bus may match the original RID of the device, resulting in the same SID being present in the device's fwspec twice. This causes trouble later in arm_smmu_write_strtab_ent() when we wind up visiting the STE a second time and find it already live.

Avoid the issue by giving arm_smmu_install_ste_for_dev() the cleverness to skip over duplicates. It seems mildly counterintuitive compared to preventing the duplicates from existing in the first place, but since the DT and ACPI probe paths build their fwspecs differently, this is actually the cleanest and most self-contained way to deal with it.

---
 drivers/iommu/arm-smmu-v3.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

@@ -1582,7 +1582,7 @@ static __le64 *arm_smmu_get_step_for_sid
 
 static int arm_smmu_install_ste_for_dev(struct iommu_fwspec *fwspec)
 {
-	int i;
+	int i, j;
 	struct arm_smmu_master_data *master = fwspec->iommu_priv;
 	struct arm_smmu_device *smmu = master->smmu;
 

@@ -1590,6 +1590,13 @@ static int arm_smmu_install_ste_for_dev(
 		u32 sid = fwspec->ids[i];
 		__le64 *step = arm_smmu_get_step_for_sid(smmu, sid);
 
+		/* Bridged PCI devices may end up with duplicated IDs */
+		for (j = 0; j < i; j++)
+			if (fwspec->ids[j] == sid)
+				break;
+		if (j < i)
+			continue;
+
 		arm_smmu_write_strtab_ent(smmu, sid, step, &master->ste);
 	}
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/iommu-arm-smmu-v3-cope-with-duplicated-stream-ids.patch queue-4.9/iommu-arm-smmu-v3-don-t-free-page-table-ops-twice.patch